Method and arrangement for obtaining perfect high vacuums



S. LOEWE Aug. 27, 1929.

METHOD AND ARRANGEMENT FOR OBTAINING PERFECT HIGH VACUUMS Filed Nov. 14,1927 Jzzven for Patented Au 2,7 1929.

TES'

PATENT OFFICE,

SIEGMUND LOEWE, OF BERLIN, GERMANY.

METHOD AND ARRANGEMENT FOR OBTAINING PERFECT HIGH VACUUMS.

Application filed November 14, 1927, Serial No. 233,280, and in GermanyNovember 11, 1926.

This invention relates to a method of evacuating hollow glass vessels,such, for example, as thermionic valves or vacuum tubes for radiotransmission and reception.

IVith the present methods'and devices employed for evacuating suchvessels, very good results can be obtained and a high vacuum. produced,but, owing to certain difficulties present during the sealing of thetube, gases are evolved and a certain proportion of these gases passinto the vessel and reduce the vacuum to an undesirable extent.

'The object of the present invention is to provide a method whereby,after the usual exhausting action is completed, but before disconnectionof the vessel from the exhausting device, and while the latter is stillacting, communication between the vessel and the exhausting devicemay becut off so as to prevent passage of any residual gases remaining in theexhaust tube, or of any gases evolved during the sealing process, frompassing in any material amount into the vessel.

The principle underlying my invention will be more fully understood byreference to the accompanying drawing, in which Fig. 1 is a sectionalview through a thermionic valve, showing the bulb as it appears priorto, evacuation and sealing and illustrating one mode of closingcommunication between the bulb and exhaust pump prior to the bulbsealing action.

Figs. 2 and 3 are views showing other ways of carrying the inventioninto practical efiect. 1

- The hollow v glass vessel illustrated comprises a thermionic bulb Rhaving at one end a pedestal F to support a system of elec-. trodes S. Pis the exhaust tube integral with the other end of the bulb and providedfor the connection therewith of the exhaust pump or device. It may beassumed that the bulb and the system of electrodes have been completelyfreed fromair andevacuated by the well known process. The degree ofvacuum is, however, reduced by gas freed and :evolved durin theoperation of heating and contracting t e .tube at point A v to sealthebulb. Some of this gas thus set free will under present processes passinto the bulb R, and the ob ect of the pre'sent invention is to preventthis or to reduce to a material extent the quantity of gas which mayunavoidably enter-the bulb Mere- 1y for illustrating the principle of myinvention it may be assumed that inside the bulb a round disc G of micaor other suitable material is placed which, under normal conditions, isarranged adjacent to but out of alinement with the exhaust port Ecommunicating with the tube P. When the extraction of gas has beencompleted, then accordmg to my invention this port is closed by movingdisc G so that it will be drawn into the port to tightly fit the same bythe suction of the pump., Although this sealing may filled with the gasset free during the fusing.

under the steam pressure which has prevailed during the fusing. This gaswill gradually pass into the bulb R, but such amount of gas isinconsiderable owing tothe small area of the space H.

After the explanation of the principle made by reference to Fig. 1,Figs. 2 and 3', may illustrate two practical embodiments of theprinciple underlying my invention. The portion of the exhaust tube whichis to be hermetically sealed to close bulb R has in this case been'givena conical shape at K. Inside the bulb is a movable closure member whichmayxconsist of a thin-walled small lass stem T which at its upper endhas been blown to form a funnel-shaped stopper T'.. After completion ofthe pumping operation the stopper T is allowed to drop down so that itfits loosely into the conical part K of the bulb. It thenclosescommunication between the bulb R and the pump P, leaving only avery-small hollow space remaining in the tubev between the stopper andthe bulb. In the operation of fusing and sealin the tube the stem T andstop er T'- are used to the sealed portion of t e tube, and the excessportion of the stemis severed with the excess portion of the tube beyondthe sealing point A. In order to prevent the stopper T from moving fromopen position to closed position during the pumpmg operation, the outerend of the stem T may be provided with a* part N of nickel, iron orother metal capable of being attracted by a magnet M held during thepumping operano her so as to keep the that only a very tion at a levelto support the closure memstopper in open position as shown in Fig. 2.Upon the completion of such operation the magnet M is lowered to allowthe closure member or 'moved away from the tube to break the magneticattraction and drop and the close communication between the bulb andtube. The fusing of the stopper T to the sealed nub of the tubeincreases the strength of the tube at this point.

A further and "in practice particularly simple embodiment is illustratedin Fig.- 3. In this case a glass stopper disc' T is carried by a stem Hand this disc is firmly held in the exhaust tube in the proximity'of itsfusing point in such manner that during the. pumping operation asuificiently wide intervening space or aperture 0 exists. Aftercompletion of the pumping operation, the glass wall of the exhaust tubeis heated and contracted to close it to such an extent small apertureremains.

-- During this voperation the wall of the exhaust tube may be fused tothestopper T except at a point alining with such small aperture. This-man1pulation .having been performed, the fusing point proper A is Iheated and drawn together, thus sealing the tube and the aperturereferred to, but, if desired, the aperture may be closed prior to thesecond heating of the tube by allowing the tube to contract by coolingabout the stopper, as will be readily understood.

Having thus.describedmy invention, 1 claim 2-- I I 1. The method ofevacuating hollow glass vessels of that pc in which the vessel is,rimarily, provi ed with anexhausttube\ or connection with the exhausterduring\ the evacuating period 'and designed to be ion o sealed by fusionon complet the evacustopper T to seat and ating action,

the vessel and the tube when the vessel is e hausted to the desireddegree but while the tube is connected with the exhauster and theexhauster is still in action, and then sealing the tube.

primarily provi for connection with the exhauster during the evacuatingperiod and designed to be sealed by fusion on completion of theevacuating action, which consists in bringing means into position forclosing communi cation between the vessel and the tube when whichconsists in closing 'communication" between 2. The method of evacuatinghollow glass vessels of that t pe in which the vessel is ed with anexhaust tube the vessel is exhausted to the desired'degree but while thetube is connected with the exhauster'and the exhauster is still. inaction, and then sealing the tubeand simultaneous] fusing the clos1n-means thereto. Y

3. The method of evacuating hollow glass vessels of that typem which thevessel is primarily provided with an exhaust tube for connection withthe exhauster during the evacuating period and designed to be sealedbyfusion on completion of the evacuating action, which consists in ilycontracting the exhaust tube between the exhausterand vessel andadjacent to the latter, bringing means into position to close the -tubebetween the vessel and the said contracted portion when the vessel isexhausted to the desired-degree but while the tube is connected with.the exhauster and preliminarthe exha'uster is still in action, and thenfurther contracting and fusing the contracted portion of the tube andsimultaneously fusing the closing means thereto.

Intestimony whereof I have aflixed my signature. v

' sineMoND LoEwE.

